ES2693157T3 - Semi-hermetic compressor motor for ammonia service - Google Patents

Abstract

A semi-hermetic compressor (40) comprising a compressor part (14) and an engine (12) enclosed in a housing part (16); the compressor part (14) configured to compress a working fluid (24), and which is driven by the motor (12); the motor (12) comprises a plurality of field windings; a plurality of motor cables (22) that are connected to the field windings, wherein the plurality of motor cables (22) extends from an interior of the housing part (16) to an exterior of the part (16 ) housing through a passage assembly (30) mounted on the housing part (16); characterized in that the passage assembly (30) is annular and comprises a base part (28), a first insulation part (26), a second insulation part (42) and a cover part (40); wherein the base part (28) forms an airtight seal between the housing part (16) and an outer periphery of the base part (16); each of the first and second insulation parts (26, 42), comprises at least one opening for receiving and compressing a cable (22) of the insulated motor that passes through the base part (28); and a sealant (48) is disposed between the first and second insulation part (26, 42) within the base part (16), wherein the sealant (48) is epoxy, silicone or putty.

Description

5

10

fifteen

twenty

25

30

35

40

Four. Five

DESCRIPTION

Semi-hermetic compressor motor for ammonia service Background

The application generally refers to a semi-hermetic compressor engine for use with ammonia coolant. The application relates more specifically to a semi-hermetic compressor motor having copper field windings, for use with ammonia coolant.

Ammonia is a common compound that occurs naturally in the environment and is naturally broken down into hydrogen and nitrogen. Ammonia refrigeration is a cost effective and energy efficient method for processing and storing frozen and non-frozen food. Ammonia refrigeration is also used in the chemical industry. Air conditioning has been provided by ammonia refrigeration systems in office buildings, parks and small buildings, such as convenience stores.

The ammonia is electrically conductive in some conditions and corrosive to many materials, e.g. eg, the copper cable used in high efficiency electric motors. The electrical connections, p. For example, multi-conductor motor terminations that are exposed to ammonia in the environment may present a risk of short circuit or other failure. The electrical conductors must be electrically isolated and sealed with steam or ammonia liquid.

Semi-hermetic engines are not widely used in refrigeration or HVAC applications where the ammonia is the refrigerant because the insulation of the winding and the ammonia coolant are incompatible. In the past, it was believed that the copper and other yellow metals used in the manufacture of motor windings could not be used in an ammonia coolant system, because such metals would be corroded by the coolant in the presence of water.

Aluminum cable has been used in some engines used to reduce the problems associated with potential exposure to ammonia. The aluminum cable is used, for example, in on-board applications, since aluminum is more resistant to corrosion in the presence of ammonia and water. The aluminum cable reduces the efficiency of the motor due to the greater resistance of the aluminum cable than that of the copper cable. Due to the electrical conductivity of the ammonia, there can be no exposure of metal conductors to the gas stream. To avoid electrical failures, in some cases, the motor stator may be enclosed in a sealed box or the motor windings encapsulated. These insulation measures reduce the benefit of a semi-hermetic engine as the heat dissipation capacity of the windings is reduced, and external cooling may be required, or the size of the motor increased. Either method allows to reduce the heat dissipation and, consequently, to raise the winding temperatures of the motor. Current semi-hermetic engines that use aluminum windings experience an efficiency loss of approximately 4% to 5%.

A compressor according to the preamble of claim 1 is described in GB 1 468 808 A. The known compressor has a motor stator. The stator is encapsulated with an epoxy resin molding in which the motor terminals are embedded. In this way, easy repair and replacement of the terminal is difficult.

US 3 055 972 discloses a packaging construction for use in sealing an electric cable inside a housing, or through which it passes or in which it ends, so as to prevent the leakage of fluid to along the cable.

JP 2005 171 943 A discloses a hermetic compressor for ammonia coolant comprising a compression mechanism section using ammonia coolant as the working fluid and an electric motor exposed to the ammonia coolant and using a coated aluminum electrical cable with fluororesin, which are housed in a closed casing.

The expected advantages of the disclosed systems and / or methods satisfy one or more of these needs or provide other advantageous features. Other features and advantages will become apparent from the present specification.

Summary

The invention is defined by independent claim 1. The dependent claims define advantageous embodiments.

A semi-hermetic compressor is applied to a cooling system with ammonia as working fluid. The motor 5 is exposed to the ammonia refrigerant inside a semi-hermetic housing and is cooled by the ammonia refrigerant moving through the compressor. Ammonia can be used in refrigeration and air conditioning systems because it is a natural refrigerant compatible with the environment. Ammonia has a very good cycle efficiency and a low power-cooling ratio. Using a semi-hermetic engine for this purpose has the economic benefit, performance and elimination of a shaft seal that is a potential source 10 of leakage into the atmosphere. The semi-hermetic engine can be operated at higher speeds than a conventional air-cooled engine, because the rotor of the engine can be installed on the existing compressor bearings. Since these bearings are normally lubricated with oil mist instead of lubricated with grease, as is normally the case in a separate air-cooled motor, they can operate at much higher speeds, thus reducing the size and cost required for the compressor and the compressor. engine. Therefore, the compressor can have a more compact packing arrangement than open-thrust motors and compressors, which require more space and cost. Therefore, the semi-hermetic engine reduces the size, weight and cost of the compressor and the engine. The semi-hermetic motor is suitable for the operation of the frequency inverter (VFD) as a result of the increase in operating speeds and the reduction in costs associated with semi-hermetic engines.

Certain advantages of the embodiments described herein include the use of copper windings in the semi-hermetic motor with ammonia environment to increase the efficiency of the motor.

Another advantage is that the semi-hermetic motor with copper windings can be used for various HVAC or refrigeration applications, including coolers charged with ammonia.

Alternative exemplary embodiments relate to other features and combinations of features that may be recited generally in the claims.

Brief description of the figures

FIG. 1 shows a cross-sectional view of an example semi-hermetic compressor having a sealed motor connector.

FIG. 2 shows a partial detail in enlarged cross-section of the semi-hermetic compressor indicated by section B in FIG. one.

FIG. 3 shows a partial enlarged cross-sectional view of the electrical penetration seal indicated by section C in FIG. two.

Detailed description of the example embodiments

Referring first to FIGs. 1 and 2, a semi-hermetic compressor 10 includes a motor 12 and a compressor part 14. A semi-hermetic housing 16 encloses both the compressor part 14 and the motor 12. The motor 12 includes a stator 20 arranged around a magnetic core or rotor 18. The rotor 18 is made of steel laminations that generate magnetic fields when the motor 12 is energized When a three-phase AC supply is applied, the magnetic field advances from one stator winding to the next, causing the magnetic field to rotate and drive the rotor 18. An electric step assembly 30 is provided at one end of the motor 12 40 adjacent to the motor. Semi-hermetic compressor 10. The passage assembly 30 provides a sealed conduit for the wires 22 of the field coil to pass through the housing 16 to the external atmosphere, where the individual field coil wires can be coiled or otherwise joined to form various configurations of star winding, triangle or star-triangle. The external connections can be made in a non-corrosive atmosphere or less corrosive than the ammonia coolant 24 contained within the housing 16.

45 Referring next to FIG. 3, an example step set 30 is shown. In one embodiment, the passage assembly 30 may be a compression-type accessory that seals air passages around the outside of the cable and also compresses the insulation of the cable around the individual cables to prevent refrigerant leaks along the path of the cable through which it passes through the set 30 to the outside atmosphere. The wires 22 of the field coil extend from the stator 20 through the passage assembly 30, first into a first cylindrical insulating part 26 disposed within an annular base 28. The first part 26 insulator provides

5

10

fifteen

twenty

25

30

35

40

Four. Five

fifty

a hermetic seal between an outer surface of the insulating part 26 and an inner ring 29 of the base 28. The first insulating part 26 includes openings 32 for receiving the wires 22 of the field coil therethrough. The base 28 is removably secured to the housing 16 by a hermetic connection, e.g. eg, by means of a threaded fitting, a quick disconnect fitting or a similar accessory which are well known in the art. The base 28 may include a hexagonal or rectangular half segment 34, an internal connector portion 38 and an external connector portion 36. The middle segment 34 provides a surface for applying a tool for connecting or removing the base 28. The internal connector portion 38 extends into the housing 12 and the external connector portion 36 extends from the middle segment 34 to receive a portion 40 of cover. The lid part 40 is attached to the external connection part 36, p. eg by means of a screw thread accessory, a quick disconnect accessory device or the like. A second insulating part 42 fits perfectly within the annular opening 44 through the second insulating part 42 to provide a hermetic seal therebetween. The second insulating part 42 includes a plurality of openings 46 corresponding to the openings 32 in the first insulating part 26.

According to the invention, a sealant 48, p. eg, epoxy, silicone or putty, applied in the space between the insulators 42, 26 to seal any voids that may be present around the wires 22 of the field coil or the inner ring 29. In addition, an anti-rotational element 50 may be provided adjacent the lid portion 40 to prevent rotation of the lid portion 40 relative to the base 28.

A conventional three-phase motor can have multiple individual field winding wires (not shown) which are crimped together to form a motor cable 22 extending from the motor 12. The external power connections are made to the motor cable 22, eg . eg, in a connection box or other connection box outside the housing 16. In the case of a three-phase motor, at least three cables 22 of the motor are present, depending on the configuration of the motor windings. The star connection, the triangle connection or the star / triangle connection are examples of various stator winding configurations. The electrical connections within the motor 12 to the external power source result in at least a portion of the motor cables 22 being potentially exposed to a working fluid, e.g. eg, ammonia refrigerant. All power connections can be made outside the pressure limit defined by housing 16 to prevent exposure of the cable to the refrigerant.

Working fluids or coolants that have a low electrical conductivity do not present a problem with electrical short circuits through exposure to the motor cables 22 or other electrical conductors. However, ammonia is characterized by a higher electrical conductivity than other working fluids and coolants, so when ammonia is used for the working fluid, the exposed cables or connections of the motor will cause a short to ground.

The insulation of the cable used for the stator 20 and the motor cables 22 must be suitable for use with ammonia liquid, ammonia gas and lubricant used in the refrigeration system. This effectively insulates the individual field coil cables and allows the motor to operate in the ammonia environment, but also provides the additional benefit of using yellow metals, e.g. eg, copper, in the motor windings. The engine will have the same efficiency seen in use with other more common HCFC, HFC or HFO refrigerants.

The motor windings and the copper wire can be used with the step connector described above, provided that the electrical insulation is adequate to prevent the exposure of the motor cable to the ammonia and the motor cables can be secured to prevent the infiltration of the motor itself. cable is exposed to ammonia. If the insulation is permeable and a small amount of ammonia finds its way to the surface of the cable, the cable itself will not disintegrate. Copper cable may begin to corrode, but corrosion does not inhibit the current carrying capacity of motor conductors or windings. If corrosion occurs, there is only a slight corrosion accumulation slip and, as such, there is no degradation of the cable, or the conductive quality of the cable or its magnetic properties. If the water is allowed to mix with the ammonia, even in relatively small percentages, the mixture corrodes the copper wire quickly. Therefore, it is important that the insulation system protect the cable from exposure to any mixture of water and ammonia circulating in the system. Filter dryers can be used in the ammonia system to capture and contain any water that mixes with the ammonia during normal charging with refrigerant and service. This will reduce any corrosion potential of the copper cable. However, once the insulation system is broken, the electrical conductivity of wet ammonia can generally cause the motor control to be protected to prevent operation due to the short circuit of the electrical input to the motor.

While the exemplary embodiments illustrated in the figures and described herein are currently preferred, it should be understood that these embodiments are offered by way of example only.

It is important to note that the construction and disposition of the semi-hermetic ammonia compressor with a sealed passage connector as shown in the various exemplary embodiments are only illustrative. Although only a few embodiments have been described in detail in this disclosure, those reviewing this disclosure will readily appreciate that many modifications are possible (eg, variations in sizes, 5 dimensions, structures, shapes and proportions of the various elements, values). of parameters, assembly arrangements, use of materials, colors, orientations, etc.) without departing materially from the teachings and novel advantages of the subject matter described in the claims. For example, the elements shown as integrally formed can be constructed of multiple parts or elements, the position of the elements can be reversed or otherwise varied and the nature or number of discrete elements or positions can be altered or varied.

Claims (10)

5 10 fifteen twenty 25 30 35 40 Four. Five A semi-hermetic compressor (40) comprising a compressor part (14) and a motor (12) enclosed in a housing part (16); the compressor part (14) configured to compress a working fluid (24), and which is driven by the motor (12); the motor (12) comprises a plurality of field windings; a plurality of motor cables (22) that are connected to the field windings, wherein the plurality of motor cables (22) extends from an interior of the housing part (16) to an exterior of the housing part (16) through a passage assembly (30) mounted on the part ( 16) of housing; characterized by that the passage assembly (30) is annular and comprises a base portion (28), a first isolation portion (26), a second isolation portion (42) and a cap portion (40); wherein the base portion (28) forms a hermetic seal between the housing part (16) and an outer periphery of the base portion (16); each of the first and second insulation portions (26, 42) comprises at least one opening for receiving and compressing an insulated motor cable (22) passing through the base part (28); Y A sealant (48) is disposed between the first and second insulating part (26, 42) within the base part (16), wherein the sealant (48) is epoxy, silicone or putty. 2. The compressor of claim 1, wherein: the first isolation part (26) is configured to fit within an annular opening in the base part (16); or wherein the lid part (40) can be removably attached to the base part (28); or wherein the step assembly (30) is a compression-type accessory, configured to seal around an outer surface of the motor cable (22) and to compress a cable insulation around an individual cable of the cable (22) of the cable. motor to prevent refrigerant leaks along the cable (22) of the motor where the cable (22) of the motor passes through the assembly (30) to an external atmosphere. 3. The compressor of claim 1, further comprising an anti-rotation element disposed between the lid part and the base part to prevent relative rotation between the lid part and the base part. The compressor of claim 1, wherein the plurality of wires (22) of the field coil extends from a stator (20) of the engine (12) through the set (30) of passage to the first part ( 26) of insulation disposed within the base part (28). 5. The compressor of claim 1, wherein the base part (28) can be removably secured to the housing part (16) by means of a threaded fitting or a quick disconnect attachment; or wherein the base portion (28) further comprises a middle segment (34), an internal connector portion (38) and an external connector portion (36). 6. The compressor of claim 5, wherein the middle segment (34) comprises a hexagonal or rectangular configuration with at least one surface for applying a tool for connecting or removing the base part (28); or wherein the inner connector part (38) extends within the housing part (16) and the external connector part (36) extends from the middle segment (34) and receives a lid part (40). The compressor of claim 6, wherein the lid part (40) is configured to engage with the external connector part (36) by means of a threaded fitting or a quick disconnect fitting. The compressor of claim 1, wherein the second isolation portion (42) includes a plurality of openings corresponding to the openings in the first isolation portion (26). The compressor of claim 1, further comprising an anti-rotation element (50) adjacent to the lid part (40), the anti-rotation element (50) configured to prevent rotation of the lid part (40) with respect to the base part (28). The compressor of claims 1-9 above, wherein the working fluid (24) is ammonia.